In some applications of image sensor chips, two cameras are needed to obtain images from opposite directions. For example, mobile devices such as mobile phones may include two cameras on opposite sides. Two image sensor arrays facing opposite directions are thus needed to sense images.
The two image sensor chips were bonded to a same Printed Circuit Board (PCB). Since certain distance needs to be maintained to separate each of the image sensor chips from the respective focal lens, the thickness of the mobile application cannot be smaller than a combined thickness of the thickness of the PCB, the thicknesses of two image sensor chips, and two times the distance between the image sensor chips and the respective focal lens. Besides, the two image sensor chips need to have separate footprints, and cannot be placed on the PCB back-to-back and aligned to each other since each of them needs to route signals to and from the PCB.